From fe8794560a22cc62a482bf071e2050ce1ea6ea3e Mon Sep 17 00:00:00 2001
From: Anatoli Papirovski <apapirovski@mac.com>
Date: Tue, 1 May 2018 13:32:10 +0200
Subject: [PATCH] events: optimize condition for optimal scenario
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Instead of always checking whether we've already warned about a
possible EventEmitter memory leak, first run the rest of the
code as accessing random properties on an Array is expensive.

In addition, remove an unnecessary truthy check.

PR-URL: https://github.com/nodejs/node/pull/20452
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
---
 benchmark/events/ee-add-remove.js |  2 +-
 lib/events.js                     | 30 ++++++++++++++----------------
 2 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/benchmark/events/ee-add-remove.js b/benchmark/events/ee-add-remove.js
index eee8ff4524ed1a..54e680f74ae3e1 100644
--- a/benchmark/events/ee-add-remove.js
+++ b/benchmark/events/ee-add-remove.js
@@ -2,7 +2,7 @@
 const common = require('../common.js');
 const events = require('events');
 
-const bench = common.createBenchmark(main, { n: [25e4] });
+const bench = common.createBenchmark(main, { n: [1e6] });
 
 function main({ n }) {
   const ee = new events.EventEmitter();
diff --git a/lib/events.js b/lib/events.js
index 46d1223e69a4bf..ff1648d6aa13e7 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -235,22 +235,20 @@ function _addListener(target, type, listener, prepend) {
     }
 
     // Check for listener leak
-    if (!existing.warned) {
-      m = $getMaxListeners(target);
-      if (m && m > 0 && existing.length > m) {
-        existing.warned = true;
-        // No error code for this since it is a Warning
-        // eslint-disable-next-line no-restricted-syntax
-        const w = new Error('Possible EventEmitter memory leak detected. ' +
-                            `${existing.length} ${String(type)} listeners ` +
-                            'added. Use emitter.setMaxListeners() to ' +
-                            'increase limit');
-        w.name = 'MaxListenersExceededWarning';
-        w.emitter = target;
-        w.type = type;
-        w.count = existing.length;
-        process.emitWarning(w);
-      }
+    m = $getMaxListeners(target);
+    if (m > 0 && existing.length > m && !existing.warned) {
+      existing.warned = true;
+      // No error code for this since it is a Warning
+      // eslint-disable-next-line no-restricted-syntax
+      const w = new Error('Possible EventEmitter memory leak detected. ' +
+                          `${existing.length} ${String(type)} listeners ` +
+                          'added. Use emitter.setMaxListeners() to ' +
+                          'increase limit');
+      w.name = 'MaxListenersExceededWarning';
+      w.emitter = target;
+      w.type = type;
+      w.count = existing.length;
+      process.emitWarning(w);
     }
   }